The present invention relates generally to a composite materials design process. More specifically, the present invention relates to a knowledge driven composite design optimization process and corresponding system. A computer program adapted to facilitate implementation of the knowledge driven composite design optimization process is also disclosed.
The use of composites in airframe construction is becoming an increasingly complex process. Composite structures are generally designed at the local laminate level using wireframes or solids in Computer Aided Design (CAD) systems such as the UNIGRAPHICS ((trademark)) CAD system. Analysis is performed using a separate analytical model(s), e.g., a finite element based model, which initially assumes laminate families which define a percentage composition (number) of each ply orientation and which is generally coordinated with design geometry through imported master datums and a design surface. A typical design process is illustrated in the functional flowchart of FIG. 1. From the flowchart, it will be appreciated that the current design process has not been optimized. For example, finite element analysis (FEA) is conducted before the step of editing the ply lay-up for manufacturability, which virtually guarantees that the FEA step will have to be repeated and, in many cases, repeated several times. Moreover, it will be appreciated that changes in, for example, the wireframe model will require updates to, or recreation of, the finite element model and vice versa.
Furthermore, many design considerations are routinely addressed during the composite design process. For example, often in the analytical model, the order in which each oriented ply is found within the total number of plies is not considered. Typically, the analyst does not restrict the thickness map to xe2x80x9cbuildablexe2x80x9d thicknesses of the material selected or specify families which produce xe2x80x9cfabrication friendlyxe2x80x9d designs. These modifications are typically integrated by the designer in their geometry model. However, since the abovementioned modifications occur after the bulk of the analysis has been completed, there are often surprises, e.g., higher than expected component weight, at a point well into the design process. In addition, even when the analyst does define local stacking sequences, the analyst accomplishes this by performing optimizations which result in local laminate definitions which do not integrate well with one another.
It will also be noted that documentation for manufacturing is currently provided in two key ways:
(1) as a design surface with cured ply boundaries projected to a plane; and
(2) through manually created section cuts and laminate tables that contain text entities for each ply identifying orientation, material and number of each ply.
Since the textual data must be created manually, text data having missing information is frequently released to other manufacturing departments. When design changes occur, these errors and omissions are compounded because the text data is often only partially updated after each design change.
The inner moldline, which is often a tooled surface and always a structural mating surface, is defined by conceptually joining the resultant section cuts of the engineering, i.e., CAD, definition. Manufacturing personnel then flatten the ply geometry to create uncured ply boundaries that are cut for fabrication. Translation errors due to selection of the incorrect normal orientation during this step are a common occurrence when working with complex geometry, primarily because standards do not address this level of detail. Moreover, while the thickness of the composite material used to create the laminate is 18-25% thicker than cured material, this fact is normally not reflected in any of the traditional models. It should be mentioned that the one exception to this general statement is found in the unique files which are created by manufacturing for laser projection that use a xe2x80x9cdebulkedxe2x80x9d ply thickness to develop a three dimensional (3-D) plies representation of the part in the lay-up step of fabrication. The variability of the translation process is high, since design intent is not always clear because all ply boundaries are represented on one 3-D plane rather than in true 3-D space. An example of the type of defect created with no geometrical definition at the ply level in 3-D space is described immediately below.
The lack of geometrical accountability for ply overlaps leads to locally undersized areas in tools. This in turn results in increased local pressure on the component during the cure at ply overlap or splice areas. This may contribute to internal laminate defects in the form of porosity or resin poor areas in a structure if enough of these details occur through the thickness in an area. In addition, lack of geometrical accountability can lead to local distortion of the fiber architecture and can result in increased interlaminar shear stress, each of which adversely affects structural performance. These cause and effect relationships are viewed as too complex for the current conventional composite process to track and control during design and fabrication. It will be appreciated from the references, discussed briefly below, that a great deal of attention is paid to these effects at the micromechanics level in literature and in the typical fabrication shop for specific structures, yet no standard process allows easy incorporation of these considerations into composite design practices. The current approach to understanding these local effects is to build and then cutup composite parts, i.e., to perform destructive testing of the articles. It will be appreciated that this is an expensive and time-consuming approach to understanding a geometrical problem.
In addition, manufacturing constraints such as material width restrictions are not incorporated or reflected in the design data. Such design constraints are often considered only as a refinement (iteration) within the manufacturing definition cycle, i.e., when editing ply definition to ensure manufacturability. It will be noted that this results in additional ply splices which may not be accounted for in the design. While this often leads to structural degradation, these manufacturing constraints may not be reviewed during the design steps in current practice. Thus, the analytical community is forced to adopt conservative analysis approaches to avoid the risk created by uncertainties arising from manufacturing constraints. The most common impacts of this approach are greater structural weight, more stringent fabrication requirements, and, of course, higher costs. The lack of understanding of the structural design impacts on fabrication also leads to inconsistent disposition of discrepant fabrication events, since a xe2x80x9cpreferredxe2x80x9d or xe2x80x9cbestxe2x80x9d practice has never been identified. The impacts are considered part of the variability that leads to the reduced material allowables used for composite analysis.
It should also be mentioned that design changes often require updates to manufacturing data. Manufacturing recreates the textual data at least twice to produce data forms that meet the needs of the manufacturing database. The composite database becomes the source for all in-process inspections and fabrication. Final parts are inspected to design data as prepared by manufacturing personnel in their templates and database. Database coordination for design changes is a challenging, not to mention a continuous, process.
Moreover, the only software tool that attempts to integrate the definition and analysis of composites is the Northrop Grumman""s, formerly Vought Aircraft Company""s, Computerized Composite Development Project (CCDP) program. The CCDP program is limited in that it does not create a 3-D product definition, is hard coded in FORTRAN to run on a VAX computer or computer cluster, and includes no adaptive knowledge or objects that can assist the designer in tracking sensitivities of design changes. Moreover, the CCDP program is not focused on visualization, parametric definition, or 3-D design capabilities. While the CCDP program does a relatively good job of integrating manufacturing data needs into the program and outputting documentation, the CCDP program simply cannot provide any documentation in the form of blueprints or other visual aids. In addition, the CCDP program is unable to duplicate the optimum laminate selection of an analyst without manual intervention.
What is needed is a process for designing composites which establishes a global, manufacturable laminate definition at the ply level. Additionally, what is needed is a knowledge driven composite design optimization system to automate the composite design optimization process and output of three dimensional (3-D) laminated composite designs which parametrically link laminates, plies and analysis routines, these routines are developed with a product life-cycle view which inserts heuristic information onto the object oriented structure. Preferably, object naming conventions would be used in the knowledge driven composite design optimization system to help maintain efficient association between parameters of mating structures with knowledge to help define the associations and rules to process requirements within the product life cycle.
Based on the above and foregoing, it can be appreciated that there presently exists a need in the art for a knowledge driven composite design optimization process and corresponding system which overcomes the above-described deficiencies. The present invention was motivated by a desire to overcome the drawbacks and shortcomings of the presently available composite design and fabrication technology, and thereby fulfill this need in the art.
One object of the knowledge driven composite design optimization process according to the present invention is to provide a composite design optimization process wherein all subroutines included in the process are parametrically linked to one another. According to one aspect of the present invention, the resultant composite laminate definition is parametrically refined down to the ply level.
Another object of the knowledge driven composite design optimization process according to the present invention is to provide a composite design optimization process wherein xe2x80x9cbest practicexe2x80x9d rules for composite laminate design are incorporated into the individual subroutines of the composite design optimization process. According to one aspect of the present invention, the xe2x80x9cbest practicexe2x80x9d rules are applied in a predetermined sequence to permit generation of at least one optimal design solution.
Still another object of the knowledge driven composite design optimization process according to the present invention is to provide a composite design optimization process wherein manufacturing constraints for a part are considered as soon after the part geometry is defined as possible.
Yet another object of the knowledge driven composite design optimization process according to the present invention is to provide a composite design optimization process wherein the ply connectivity between constant thickness laminate regions included in a part is globally optimized for the part. Moreover, the composite design optimization process beneficially generates optimal ramp or thickness transition features responsive to the globally optimized region connectivity. According to one aspect of the present invention, connectivity is optimized for variables including part weight, ply size and overall part strength.
Another object of the knowledge driven composite design optimization process according to the present invention is to provide a composite design optimization process capable of presenting the intermediate stages of, and resultant, laminate design in several different formats to facilitate understanding of the laminate design at the ply level by all members of the laminate design team.
A still further object of the knowledge driven composite design optimization process according to the present invention is to provide a composite design optimization process wherein intermediate stages of the laminate design can be stored for later display and reuse. It will be appreciated that this feature according to the present invention permits the laminate design team to perform tradeoff studies during the laminate design. Moreover, this feature facilitates later update of the knowledge base, e.g., the xe2x80x9cbest practicexe2x80x9d rules.
The knowledge driven composite design optimization process and corresponding system, particularly Parametric Composite Knowledge System (PACKS), advantageously addresses the high cost and cycle time of composite laminate definition. It will be appreciated that one cause of this problem stems from the fact that there are currently many different tools, i.e., programs, for design and analysis of laminates, none of which is completely parametric or associative. All of these conventional design tools have different models for the same part definition, thus duplicating data in some cases, and often creating new data (that the other tools have no knowledge of) in others. A secondary problem with these conventional software tools is the lack of visualization outputs for the composite laminate ply details, which permits manufacturing personnel to misinterpret engineering design intent and necessitates refinement or recreation of engineering data.
Advantageously, PACKS addresses these problems by creating one parametric model for composite design and analysis which outputs a three dimensional (3-D) definition of the composite laminate at the ply level. The PACKS module preferably integrates several new or existing tools into one shell, linking the outputs from, for example, the UNIGRAPHICS ((trademark)) CAD program module, an analysis database, e.g., a PATRAN ((trademark)) database, and the laminate designer subroutine while incorporating a number of rules of laminate design to increase the speed of the composite definition process. Beneficially, data developed by PACKS can be fed directly into manufacturing and analysis databases, or preferably is linked into a common database which feeds all processes.
These and other objects, features and advantages according to the present invention are provided by a knowledge driven composite design optimization process for designing a laminate part. Preferably, the process includes steps for generating a globally optimized ply definition for a laminate part, and modifying the ply definition to include features of the laminate part, where the generating and modifying steps are parametrically linked to one another and are performed in the recited order as a xe2x80x9cbest practicexe2x80x9d yet are not restricted to this order. According to one aspect of the present invention, the generating step includes substeps for determining connectivity between a plurality of regions defining the laminate part, subsequently generating ramp features detailing interconnection of the regions defining the laminate part, and displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user.
These and other objects, features and advantages according to the present invention are provided by a laminate part constructed using a knowledge driven composite design optimization process including steps for generating a globally optimized ply definition for a laminate part using predetermined optimal rules of laminate design practice, and subsequently modifying the ply definition to include features of the laminate part, wherein the generating and modifying steps are parametrically linked to one another.
These and other objects, features and advantages according to the present invention are provided by a knowledge driven composite design optimization process for designing a laminate part contained within a parametric composite knowledge system (PACKS) for generating a globally optimized ply definition for a laminate part in accordance with laminate design transition rules, and including a feature module for modifying the ply definition to include features which locally modify the global ply solution, wherein PACKS and the features module are parametrically linked to one another, and wherein the knowledge driven composite design optimization process is executed in PACKS and may be refined with the features module. According to one aspect of the present invention, PACKS preferably includes a connectivity subroutine for determining connectivity between a plurality of regions defining the laminate part responsive to the transition rules, a ramp definition subroutine for generating ramp features detailing interconnection of the regions defining the laminate part, and a visualization subroutine for displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user.
These and other objects, features and advantages according to the present invention are provided by a knowledge driven composite design optimization system used in designing a laminate part, including a first device for generating a globally optimized ply definition for the laminate part in accordance with laminate design transition rules, wherein the first device includes a second device for determining connectivity between a plurality of regions defining a the laminate part responsive to the transition rules, a third device for generating ramp features detailing interconnection of the regions defining the laminate part, and a fourth device for displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user. Moreover, the knowledge driven composite design optimization system includes a fifth device for modifying the ply definition to include features which locally modify the global ply solution. Preferably, the first through fifth devices are parametrically linked one to another, and the first through fifth devices operate in numerical order.
These and other objects, features and advantages according to the present invention are provided by a computer memory storing computer readable instructions for permitting a computer system to generate a design for a laminate part, the computer readable instructions including a parametric composite knowledge system (PACKS) for generating a globally optimized ply definition for a laminate part in accordance with laminate design transition rules, PACKS includes a connectivity subroutine for determining connectivity between a plurality of regions defining the laminate part responsive to the transition rules, a ramp definition subroutine for generating ramp features detailing interconnection of the regions defining the laminate part, and a visualization subroutine for displaying views and corresponding tabular data describing the laminate part and illustrating both inter-region connectivity and the ramp features as specified by a user, and further comprising a feature module including a subroutine for modifying the ply definition to include features which locally modify the global ply solution, wherein PACKS and the features module are parametrically linked to one another, and wherein PACKS and the features module are operated in that order as a xe2x80x9cbest practicexe2x80x9d.
These and other objects, features and advantages of the invention are disclosed in or will be apparent from the following description of preferred embodiments.